SB 

7  45* 
S7&6- 


IC-NRLF 


REPORT   OH   TtiE   SPRUCiil  BUDWORM 

by 

LI.W.    Blao^inan 

Llaine  For.    Dept.    &  Maine   Igri.    Sxper.    Sta. 

1919 


•'*"«& 


REPORT  ON  THEy 

..*** 

"  .Aov" 

SPRUCE  BUDWOR 


BY 


M.  W.  BLACKMAN,  Ph.  D., 

Professor  of  Entomology, 

New  York  State  College  of  Forestry,  Syracuse  University 


Investigations  Carried  On  and  Report  Published 

BY  THE 

MAINE  FORESTRY  DEPARTMENT 

IN  COOPERATION  WITH  THE 

Forestry  Department,    University  of    Maine 

AND    THE 

Maine  Agricultural  Experiment  Station 

1919 


Aerie .  -  Forestry.  Main  Libran 


& 


THE    SPRUCE    BUDWORM. 

The  spruce  budworm  (Tortrix  fumiferana  Clemens)  is  with 
small  doubt  the  most  destructive  enemy  of  the  spruce,  fir  and 
hemlock  in  Maine.  It  is  probably  native  to  this  country  al- 
though it  is  well  known  in  England.  An  account  of  the  earliest 
known  injuries  by  the  budworm  is  given  by  Dr.  Packard  in 
which  he  establishes  the  probability  that  the  wide  spread  de- 
struction of  spruce  in  the  Casco  Bay  region  in  1807  was  due  to 
this  insect  pest.  However  this  may  be,  it  is  certain  that  it  was 
responsible  for  the  death  of  a  large  percentage  of  the  red  spruce 
in  this  same  region  and  also  in  many  other  localities  along  the 
coastal  area  of  Maine  from  Portland  to  Rocklaiid,  in  an  infesta- 
tion which  reached  its  apex  in  1878  and  1879.  This  outbreak 
so  far  as  we  know,  was;  confined  to  the  islands  and  coastal  area 
and  did  not  extend  inland  any  great  distance.  Following  this 
great  destruction,  the  insect  seems  to  have  disappeared  so  far  as 
attracting  any  general  attention  is  concerned  for  a  period  of 
more  than  thirty  years.  However,  since  1911  numerous  enquir- 
ies and  complaints  of  its  depredations  have  been  received  both 
by  the  Entomologist  of  the  Maine  Agricultural  Experiment  Sta- 
tion and  by  the  Department  of  Forestry. 

The  present  outbreak  seems  to  be  a  much  more  serious  and 
destructive  one  than  that  of  thirty  years  ago,  for  its  extent  com- 
prises not  only  the  coast  regions  but  practically  every  wooded 
area  of  the  state.  Indeed,  by  far  the  greatest  amount  of  damage 
has  occurred  in  the  inland  portions  of  the  state,  especially  in 
Somerset,  Piscataquis,  Aroostook  and  Washington  Counties  in 
regions  remote  from  the  coast  and  covered  with  dense  forests 
of  spruce,  balsam,  fir  and  mixed  hardwoods.  From  enquiries 
sent  in  to  the  Experiment  Station  and  the  Department  of  Fores- 
try, from  reliable  information  from  various  sources,  and  from 
personal  observation,  it  is  certain  that  the  insect  was  present  to 
an  alarming  extent  in  Franklin,  Cumberland,  Lincoln,  Piscata- 
quis, Penobscot,  Waldo,  Knox,  Aroostook,  Washington  and  Han- 
cock Counties.  It  is  also  certain  that  it  was  to  be  found  in  Ox- 
ford, Somerset  and  Sagadahoc  Counties,  and  almost  as  certainly 
in  the  remaining  three  counties  of  the  state.  However,  the 


^95952 


greatest  damage  was  done  in  the  great  inland  spruce  and  balsam 
forests  of  the  northern  half  of  the  state  which  are  the  main 
source  of  supply  for  the  pulp  mills. 

Usually  one's  attention  is  first  attracted  to  this  insect  in 
the  spring  or  early  summer  by  the  wilted  or  blighted  appearance 
of  the  new  growth  at  the  ends  of  the  branches  and  twigs  of 
spruce  and  balsam.  This  has  often  been  described  as  resembling 
the  effect  produced  by  the  passage  of  a  light  fire  through  the 
woods.  If  these  blighted  tips  are  examined  they  will  be  seen 
to  be  made  up  of  the  ends  of  the  needles  or  leaves  of  the  new 
spring  growth  which  has  been  gnawed  through  at  the  base, 
but  are  still  held  loosely  together  by  a  silken,  web-like  substance. 
If  one  of  these  loose  masses  is  opened,  one  or  several  caterpillars 
are  likely  to  be  found  within.  These  are  the  culprits  responsible 
for  the  damage.  Each  when  about  full  grown  is  from  one-half 
to  three-quarters  of  an  inch  long,  with  dark,  nearly  black  head 
and  with  body  of  a  general  brown  color,  more  or  less  diffused 
with  green  at  the  sides.  Each  segment  has  several  light  colored 
warts,  dark  at  the  center  from  which  arises  a  hair.  The  insect 
begins  feeding  in  the  spring  soon  after  the  development  of  the 
new  needles  and  as  they  eat  only  the  bases  of  these,  the  entire 
new  growth  is  usually  destroyed  before  the  caterpillar  reaches 
its  full  size  about  the  middle  of  June.  The  uneaten  portions  of 
the  leaves  are  held  together  by  means  of  a  silken  thread  spun  by 
the  larvae,  which  thus  forms  a  loose  but  more  or  less  complete 
covering  or  shelter  in  which  it  remains  at  all  times.  If  all  of 
the  new  growth  is  destroyed  before  the  larvae  becomes  full  fed, 
it  extends  its  operations  toward  the  base  of  the  twig  and  feeds 
upon  the  older  needles. 

The  larvae  are  usually  full  grown  during  the  first  half  of 
June,  and,  still  in  their  loose  shelter  of  gnawed-off  needles,  trans- 
fers forms  to  pupae.  These,  in  the  course  of  the  next  week  or  two, 
give  rise  to  medium  sized,  brownish-gray  moths,  which  in  infest- 
ed regions  are  flying  in  numbers  during  the  last  week  in  June 
and  the  first  half  of  July.  The  moths  deposit  their  eggs  in  small 
light  green  masses  on  the  sides  of  the  needles.  These  eggs  are  fiat 
and  rather  scale  like  and  are  so  placed  that  they  form  small  oval 
masses  which  are  so  inconspicuous  as  to  escape  casual  notice. 
The  eggs  are  all  laid  before  the  last  of  July  and  the  larvae  from 
them  hatch  in  a  week  or  ten  da  vs.  These  minute  larvae  feed  for 


a  time,  but  perhaps  only  sparingly,  and  pass  the  winter  as  small 
only  partly  grown  caterpillars.  It  is  in  the  spring  and  early 
summer  that  their  appetite  seems  most  voracious  and  when  they 
do  the  greatest  damage. 

The  feeding  of  the  larvae  upon  the  developing  tips  of  spruce 
or  balsam  usually  completely  kills  them  and  as  no  more  can  be 
reproduced  until  the  following  season  the  tree  is  greatly  weak- 
ened. However,  to  completely  kill  the  tree,  it  is  necessary  either 
that  all  or  nearly  all  of  the  old  leaves  be  also  eaten,  or  that  the 
destruction  of  the  buds  shall  continue  several  seasons,  or  that 
the  greatly  weakened  tree  shall  be  attacked  by  other  insects,  such 
as  borers  which  complete  the  destruction.  Thus,  but  few  trees 
are  killed  the  first  year  of  attack  unless  complete  defoliation  both 
of  the  new  and  old  needles  has  resulted,  but  for  the  succeeding 
few  years  the  results  are  cumulative,  as  each  succeeding  crop  of 
new  leaves  is  nearly  entirely  destroyed,  while  in  the  meantime 
the  old  ones  are  being  lost  in  the  natural  way.  When,  however, 
bark  beetles  and  bark  weevils  attack  trees  already  weakened  by 
nearly  complete  defoliation,  as  has  been  recently  reported  by 
Swaine  in  Canada,  they  find  but  little  resistance  to  overcome  and 
the  trees  readily  succumb. 

In  order  to  determine  by  personal  observation  the  amount  of 
damage  done  by  the  caterpillars,  the  writer  spent  a  week  in  the 
forests  of  Piscataquis  County,  several  days  in  the  Rangeley  Lake 
region,  and  another  week  in  observation  in  the  coast  region  from 
Bangor  to  Kittery  Point.  In.  the  coast  region  the  infestation  is 
decidely  on  the  wane.  Considerable  damage  has  been  done  to 
the  rather  small  more  or  less  scrubby  spruce  upon  the  islands 
and  points  in  the  vicinity  of  Casco  Bay,  but  indications  are  that 
the  injuries  by  the  budworm  are  nearly  over  for  the  present. 
On  Harpswell  Neck,  which  was  visited  in  company  with  Profes- 
sor J.  M.  Briscoe  of  the  Forestry  Department,  many  of  the  small 
scrubby  spruce  near  the  roadside  had  been  partly  or  entirely 
defoliated  when  the  observations  were  made,  (June  28-30) ,  and 
some  were  in  a  dying  condition.  At  this  time  many  moths  were 
on  tke  wing  and  many  pupae  were  still  to  be  found  attached  to 
the  defoliated  twigs.  However,  a  large  percentage  of  the  trees 
were  only  partially  defoliated  and  will  undoubtedly  recover. 
At  several  places  the  injured  or  killed  spruce  had  been  cut  and 
converted  into  cord-wood  which  was  piled  along  the  roadside. 


6 

The  Rangeley  region  was  visited  early  iu  September  and  here 
also  the  injury  by  the  budworm  seems  to  be  on  the  decrease. 
Conclusive  evidence  of  its  presence  was  found  in  the  partly  de- 
foliated spruce  and  fir,  showing  the  characteristic  work  of  this 
insect.  In  some  cases  the  empty  pupal  skins  still  adhered  to  in- 
jured twigs.  Along  the  woodsland  trail  from  York's  Camp. 
Loon  Lake,  to  Richardson's  Camp,  Kennebago  Lake,  quite  a 
number  of  the  balsams  have  been  killed  during  the  last  several 
years,  but  a  large  percentage  even  of  the  larger  growth  had  es- 
caped. But  relatively  few  spruce  trees  were  dead,  although 
many  showed  the  effects  of  partial  defoliation  in  the  presence 
of  dead  branches  and  leaders.  The  work  of  the  caterpillar  dur- 
ing the  past  summer  (1919)  has  resulted  in  only  partial  defolia- 
tion and  in  practically  all  cases  observed ;  the  trees  will  doubtless 
recover.  Apparently  the  present  infestation  has  at  no  time  been 
disasterously  heavy  in  this  locality. 

The  observations  in  Piscataquis  County  were  made  during  the 
latter  part  of  July  in  company  with  Dr.  C.  T.  Brues,  of  the 
Department  of  Entomology  of  Bussey  Institution,  Harvard  Uni- 
versity and  Mr.  H.  B.  Shepard,  Forester  for  the  Eastern  Manu- 
facturing Company.  The  trip  was  made  by  automobile  from 
Lily  Bay  on  Moosehead  Lake,  to  the  foot  of  Chesuncook  Lake, 
thence  by  boat,  canoe  and  on  foot  through  Chesuncook  Lake, 
Round  Pond  and  Telos  Lake.  By  this  route  observations  were 
made  in  some  thirteen  townships  and  included  a  variety  of  con- 
ditions. Without  doubt  the  greatest  amount  of  damage  en- 
countered on  this  trip  was  to  be  observed  in  the  forests  at  each 
side  of  the  road  between  Lily  Bay  and  Ripogenus  Dam  in  the 
holdings  of  the  Great  Northern  Paper  Company.  In  certain 
localities,  often  of  considerable  extent,  practically  every  fir,  red 
spruce,  and  hemlock  of  any  considerable  size  had  been  killed  and 
most  of  the  younger  trees  down  to  a  heighth  of  only  a  few  feet, 
were  either  killed  or  badly  injured  and  distorted.  The  oc- 
casional white  spruces  seemed  to  have  escaped  with  no  injury  or 
with  only  minor  damages.  Indeed,  throughout  the  entire  area 
examined,  the  white  spruce  seemed  to  possess  some  degree  of  im- 
munity from  attack  and  injury  although  in  the  regions  of  Houl- 
ton  according  to  the  observations  of  Mr.  Win.  C.  Woods  reported 
by  Dr.  O.  A.  Johannsen  in  Bulletin  No.  210  of  the  Maine  Experi- 
ment Station,  the  white  spruce  was  second  only  to  the  balsam 


fir  in  susceptibility.  However,  there  can  be  no  doubt  of  the 
accuracy  of  our  observations,  and  they  are  confirmed  by  those 
of  Mr.  Shepard,  extended  over  a  much  larger  area  of  this 
region.  Indeed,  the  comparative  immunity  of  white  spruce  was 
first  pointed  out  by  him.  It  is  possible  that  some  unknown  local 
condition  may  be  responsible  for  this  difference  in  the  two 
localities. 

Several  days  were  spent  in  making  observations  in  Townships 
7  R.  12,  6  R.  11,  5  R.  11  and  6  R.  12,  all  but  the  last  of  which  are 
included  in  the  holdings  of  the  Lincoln  Pulp  Wood  Company. 
While  the  conditions  here  are  not  so  bad  as  in  the  Lily  Bay 
region,  there  is  evidence  everywhere  of  a  very  severe  and  injuri- 
ous infestation.  In  many  localities,  especially  in  the  denser  por- 
tions of  the  forests  where  conditions  have  remained  undisturbed 
by  the  lumbermen  for  years,  practically  all  of  the  larger  firs  and 
often-times  as  much  as  from  40  to  50  percent  of  the  larger  red 
spruce  have  been  killed  by  the  bud-moth  within  the  last  few 
years.  The  hemlock  has  also  suffered  a  high  mortality  and 
much  of  the  younger  growth  of  spruce  and  balsam  has  been 
severely  injured, — some  of  it  past  recovery. 

A  number  of  trees,  some  recently  dead,  others  apparently 
dying,  and  others  seriously  and  nearly  completely  defoliated, 
were  felled  in  order  to  examine  them  for  boring  insects,  either 
bark  beetles,  weevil  or  others,  which  might  follow  the  attack 
of  the  budworm  and  contribute  to  the  death  of  the  trees  weak- 
ened by  defoliation.  In  the  balsam  fir,  the  larvae  of  the  "saw- 
yer" Monohammus  scutellatus  were  nearly  invariably  found  in 
recently  killed  trees.  Some  of  these  had  doubtless  entered  the 
tree  while  it  was  still  alive  and  sappy,  but  in  a  weakened  condi- 
tion, but  the  majority  had  certainly  entered  trees  injured  past 
hopes  of  recovery.  Many  of  the  balsams,  though  by  no  means  all 
of  them,  had  been  attacked  by  the  balsam  bark  beetle  Pityok- 
teines  sparsus  Lee.  (Ips  balsumem  Lee.)  and  the  weevil  Pisso- 
des  dubius  in  the  trunk  regions,  while  the  smaller  limbs  and 
twigs  harbored  numerous  broods  of  another  sin  all  bark  beetle 
Cryphalus  balsamous  Hopk.  There  is  no  doubt  that  in  some 
cases  all  three  of  these  forms  had  entered  and  insured  the  death 
of  trees  which  had  been  much  weakened  by  the  budworm  and 
which  otherwise  might  have  recovered.  It  is  equally  certain 
that  in  the  majority  of  cases  the  trees  had  been  either  killed  or 


weakened  beyond  recovery  by  the  work  of  the  caterpillars  and 
the  beetles,  when  present,  were  secondary  enemies,  entering  trees 
already  dead  or  sure  to  die. 

Nearly  all  of  the  dead  and  dying  spruce  had  their  bark 
riddled  by  the  burrows  of  the  spruce  bark  beetle  (Polygraphus 
nifipenhis  Kirby).  Several  also  contained  the  brood  of  Dryo- 
coestes  affaber  Mannh.  (D.  piceae  Hopk.)  another  bark  beetle 
attacking  the  trunk  region,  while  the  tops  and  limbs  of  several 
had  been  attacked  by  Eccoptogaster  piceae  S.w.  The  sawyer 
Monohammus  sculeUatus  also  breeds  in  the  recently  killed  spruce 
although  not  in  such  numbers  as  in  balsam.  In  several  dying 
vpruce  examined  were  found  the  larvae  and  young  adults  of  a 
weevil  Pissodes  nigrae  living  in  bark  not  yet  dead.  There  is 
IHtle  doubt  that  several  of  these  beetles,  including  Polygraphus 
'ujipennis,  Eccoptogaster  piceae  and  Pissodes  nigrae,  often 
hasten  the  death  of  much  weakened  trees,  and  in  some  cases  at 
least,  insure  the  death  of  trees  which  would  otherwise  survive. 

One  of  the  most  encouraging  observations  made  in  connection 
with  this  infestation  is  that  the  destructive  work  of  the  budmoth 
larvae  is  decidely  on  the  decrease.  In  the  Chamberlain  Lake 
and  Telos  Lake  region  comparatively  few  spruce  trees  and  much 
lessened  number  of  balsam  trees  have  been  killed  during  the  past 
year,  when  compared  with  the  numbers  killed  in  1917  and  1918. 
Another  very  cheering  observation  is  the  recuperative  ability 
shown  by  the  spruce  especially.  Trees  which  were  known  to 
have  been  nearly  completely  stripped  last  year  and  which  then 
seemed  almost  certainly  doomed,  showed  a  much  improved  con- 
dition during  July  of  this  past  season  and  will  certainly  survive 
unless  there  is  a  recurrence  of  the  attack.  Such  a  recurrence  is 
not  probable  for  some  years  as  the  parasites  of  the  caterpillars 
together  with  other  natural  checks  seems  to  have  the  budworm 
under  control.  If  past  history  repeats  itself,  as  we  have  every 
reason  for  believing  it  will,  there  will  be  no  widespread,  serious 
injury  for  another  period  of  from  20  to  40  years.  It  is  likely, 
however,  that  during  the  next  few  years  a  few  trees  will  con- 
tinue to  be  killed  in  some  localities,  but  there  is  no  reason  to  ex- 
pect such  widespread  devastation  as  has  occurred  since  1912. 

While  it  is  undoubtedly  possible  to  control  the  bud  moth  by 
spraying  the  affected  trees  in  the  spring  with  arsenate  of  lead 
(5  Ibs.  to  100  gals,  water)  this  is  practical  only  for  ornamental 


and  park  trees.  The  best  reuslts  will  probably  be  obtained  by 
two  sprayings  at  an  interval  of  about  ten  days — the  first  to  be 
done  when  the  buds  are  just  opened  in  the  late  spring  and  before 
injury  by  the  larvae  is  evident.  In  woodlands  such  a  procedure 
is  of  course  impractical  both  from  the  standpoint  of  cost  and 
from  the  impossibility  of  penetrating  the  wilds  with  a  high 
power  spraying  outfit.  Indeed,  in  the  forests  man's  only  hope  is 
the  natural  checks  such  as  parasitic  and  predaceous  enemies 
which  nearly  invariably  in  the  course  of  a  few  years  control  any 
extraordinary  outbreak  of  injurious  insects. 

The  woodsland  owner  can,  however,  lessen  the  danger  of  the 
much  increased  loss  which  will  occur  if  the  trees  which  are 
weakened  by  the  budworm  arc  attacked  by  hordes  of  beetles  cap- 
able of  breeding  in  them  and  completing  their  destruction.  This 
he  can  do  by  using  proper  methods  in  his  logging  operations. 
If  stumps  are  cut  high  and  tops  are  not  properly  utilized  they 
serve  as  excellent  breeding  places  for  bark-beetles,  weevil,  and 
other  boring  beetles,  many  of  which  when  sufficiently  numerous 
will  attack  and  kill  weakened  or  even  apparently  healthy  trees. 
However,  if  the  stump  is  reduced  to  the  minimum,  the  top  uti- 
lized as  far  as  possible,  and  the  slash  properly  disposed  of,  there 
is  less  opportunity  for  these  injurious  insects  to  breed  and  less 
likelihood  of  their  breeding  up  to  numbers  sufficient  to  become 
notably  injurious.  In  forests  under  natural  conditions  for 
many  years,  these  insects  are  always  present,  but  in  the  north- 
eastern United  States,  except  following  windstorms,  fires  and 
lumbering  operations,  they  do  not  usually  occur  in  numbers 
sufficient  to  do  widespread  damages.  Perhaps  the  chief  reason 
why  only  a  small  percent- of  the  fir  and  spruce  in  the  Chamber- 
lain Lake  region  which  was  weakened  but  not  killed  by  the  bud- 
worm,  was  attacked  by  weevils  and  bark  beetles,  is  that  a  -con- 
siderable time  has  elapsed  since  this  locality  has  been  cut  over, 
and  the  injurious  forms  were  not  present  in  numbers  sufficient  to 
take  advantage  of  but  a  few  of  the  weakened  trees. 

Trees  killed  by  the  budworm  are  by  no  means  valueless,  as 
they  will  remain  sound  for  several  years  and  can  be  utilized  for 
pulpwood,  provided  they  are  not  riddled  by  wood  boring  insects. 
This  is  especially  true  of  the  spruce  which  seems  to  be  more 
resistant  to  decay  than  is  the  fir,  and  at  the  same  time  seems  to  be 
less  attractive  to  those  borers  which  riddle  the  wood  such  as  the 


10 

"sawyers".  A  very  large  percent  of  the  balsam  has  suffered 
from  "sawyer"  injury  and  much  of  it  will  soon  be  valueless. 
Owners  of  woodlands  in  the  regions  infested  should,  in  so  far  as 
it  is  practicable,  concentrate  their  logging  operations  in  the 
worst  affected  localities  in  an  attempt  to  utilize  as  much  as  pos- 
sible of  the  dead  spruce,  fir  and  hemlock  before  it  becomes  use- 
less. 


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DEC  141941 

LD  21-100w-7,'39(402f 

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